In vehicle manufacture, space is budgeted for the transmission system and packaging. Induction machine stators with toroidal windings offer a space savings over stators with conventional lap windings. Lap windings require end space which increase the length of the machine. End space is needed to route a coil from one stator slot to another stator slot which is several slots away according to the pitch or spacing of the coils. The end turn, the length of coil that extends from between the slots from one coil side to the other coil side, extends beyond the stator laminations thereby increasing the length of the stator by the distance required for the coil to make the turn from the slot for one side of the coil to the corresponding slot for the other side of the coil. Toroidal windings conserve space because a large turning area for end turns is not required. Toroidal coils are wound about the core with one side of the coil laid in the slot on the interior of the laminations, and the other side of the coil being laid on the outer periphery of the laminations. However, even with toroidal windings, there are end turns that extend beyond the laminations because of the space required for the coil to make the turn to go from one side of the laminations to the other side of the laminations.
In a vehicle, the alternator is subjected to constant operation generating heat which must be dissipated. Conventional toroidal windings have coils surrounding the core compounding the problem of heat dissipation because the core can not be used to dissipate coil heat as is the case with lap windings. Hot spots can exist where the coil is not in uniform contact with the core laminations. Further, toroidal coils are layered placing one layer closer to a heat sink so that heat is not transferred uniformly. Another problem with some toroidal windings is that the inner diameter of the core is smaller than the outer diameter so that spacers must be hand positioned when assembling the coils to prevent coil movement. Adding spacers during assembly complicates the assembly process and slows production.
It is desirable to have a stator with toroidal coils that have minimal end turn and promote heat dissipation.